Nicotinamide downregulates gene expression of interleukin‐6, interleukin‐10, monocyte chemoattractant protein‐1, and tumour necrosis factor‐α gene expression in HaCaT keratinocytes after ultraviolet B irradiation

Ultraviolet (UV) radiation has profound effects on human skin, causing sunburn, inflammation, cellular‐tissue injury, cell death, and skin cancer. Most of these effects are mediated by a number of cytokines produced by keratinocytes. In this study we investigated whether nicotinamide (NCT), the amide form of vitamin B3, might have a protective function in reducing the expression of interleukin (IL)‐1β, IL‐6, IL‐8, IL‐10, monocyte chemoattractant protein (MCP)‐1 and tumour necrosis factor (TNF)‐α in UV‐irradiated keratinocytes. HaCaT cells were treated with UVB in the presence or absence of NCT, and cytokine mRNA levels were examined by quantitative real‐time PCR. NCT significantly downregulated IL‐6, IL‐10, MCP‐1 and TNF‐α mRNA expression, whereas it did not exert any significant effect on IL‐1β or IL‐8 expression. Because of its ability to decrease these cytokine mediators after UV exposure, NCT is a possible therapy to improve or prevent conditions induced or aggravated by UV light.     

IL‐17A synergistically enhances TLR3‐mediated IL‐36γ production by keratinocytes: A potential role in injury‐amplified psoriatic inflammation

Skin injury can trigger formation of new lesions in psoriasis (Koebner phenomenon). The mechanisms through which injury exacerbates psoriasis are unclear. During wound repair, epidermal keratinocytes are activated and produce abundant IL‐36γ, further promoting the skin inflammation. IL‐17A is the cornerstone cytokine in the pathogenesis of psoriasis. We sought to investigate the effects of IL‐17A on injury‐induced keratinocyte activation and IL‐36γ production. Here, we demonstrated that dsRNA released from necrotic keratinocytes induced the expression of IL‐36γ. Silencing of TLR3 by siRNA decreased the IL‐36γ induction by necrotic keratinocyte supernatant. Co‐stimulation with dsRNA and IL‐17A synergistically increased the expression of IL‐36γ and other proinflammatory mediators (CCL20, CXCL8, DEFB4 and LCN2) in keratinocytes. The synergistic effects were not dependent on TLR3 upregulation, TNF receptor signalling and mRNA stabilization. Co‐stimulation with dsRNA and IL‐17A resulted in an accumulation of IκBζ. The synergistic upregulation of IL‐36γ and proinflammatory mediators were inhibited by IκBζ siRNA. Co‐stimulation with IL‐17A and poly(I:C) markedly activated the p38 MAPK and NF‐κB pathway, compared with poly(I:C). Blockade of p38 MAPK and NF‐κB suppressed dsRNA/IL‐17A–mediated IκBζ and IL‐36γ induction. These findings demonstrated that IL‐17A synergistically enhanced the dsRNA‐mediated IL‐36γ production through a p38 MAPK‐, NF‐κB–, and IκBζ‐dependent mechanism.     

Heparinoid suppresses Der p‐induced IL‐1β production by inhibiting ERK and p38 MAPK pathways in keratinocytes

Epidermal keratinocytes initiate skin inflammation by activating immune cells. The skin barrier is disrupted in atopic dermatitis (AD) and epidermal keratinocytes can be exposed to environmental stimuli, such as house dust mite (HDM) allergens. We showed previously that HDM allergens activate the NLRP3 inflammasome of keratinocytes, thereby releasing pro‐inflammatory cytokines. Heparinoid is an effective moisturizer for atopic dry skin. However, a recent report showed that heparinoid treatment can improve inflammation of lichen planus. Therefore, we hypothesized that it acts on epidermal keratinocytes not only as a moisturizer, but also as a suppressant of the triggers of skin inflammation. We found that HDM allergen‐induced interleukin (IL)‐1β release from keratinocytes was inhibited significantly by heparinoid pretreatment without affecting cell viability. However, heparinoid did not affect caspase‐1 release, suggesting that heparinoid did not affect HDM allergen‐induced inflammasome activation. Heparinoid treatment not only decreased intracellular levels of pro‐IL‐1β, but also suppressed IL‐1β messenger RNA (mRNA) expression in keratinocytes. Among the intracellular signalling pathways, the activation of extracellular signal‐regulated kinase and p38 pathways, which are required for IL‐1β expression in keratinocytes, was inhibited by heparinoid treatment. The inhibitory effect of heparinoid on IL‐1β mRNA expression was also confirmed with living skin equivalents. Our results demonstrated that heparinoid suppresses the initiation of keratinocyte‐mediated skin inflammation.     

Effects of β‐carotene on oxazolone‐induced atopic dermatitis in hairless mice

Skin acts as a barrier, which protects internal tissues and promotes moisture retention. Atopic dermatitis (AD) is an inflammatory skin disease associated with a variety of genetic and environmental factors that involve helper T cells. β‐Carotene (provitamin A) exhibits antioxidant activity and activates the immune system. However, it is not clear whether inflammation in AD skin is improved by posttreatment with β‐carotene. In the current study, we investigated the effects of β‐carotene on the skin of hairless mice with oxazolone‐induced inflammation/oedema (Ox‐AD mice). We found that skin inflammation was significantly reduced by oral administration of β‐carotene. In addition, treatment with β‐carotene suppressed protein levels of TNF‐α, IL‐1β and MCP‐1, as well as mRNA expression associated with IL‐1β, IL‐6, IL‐4 and Par‐2 in skin tissues. Furthermore, the mRNA and protein levels of filaggrin, a structural protein in the epidermal stratum corneum, were elevated by β‐carotene administration as compared with Ox‐AD mice. β‐Carotene significantly reduced the activity of proMMP‐9, but not proMMP‐2. These results suggest that in Ox‐AD mice, β‐carotene improves skin inflammation by suppressing the expression of inflammatory factors, promoting filaggrin expression and reducing MMP‐9 activity. β‐Carotene is a potent anti‐inflammatory agent that improves the barrier functions of AD skin.     

Evidence for a regulatory loop between IFN‐γ and IL‐33 in skin inflammation

Interleukin‐33 has recently gained much attention due to its role in allergic responses. It has been shown to amplify Th2 responses and to act as a damage‐associated molecular pattern. IL‐33 acts on a broad range of cells and has been proposed to link innate and adaptive features of allergic responses. It was the aim of this study to investigate this property of IL‐33 in the inflammatory response characterising atopic dermatitis (AD). We have analysed the response of skin‐resident cells derived from patients with AD and healthy donors with regard to the expression of IL‐33 and its receptor ST2. The functional impact of IL‐33 on CD4+ T cells was investigated. Keratinocytes and dermal fibroblasts clearly differ in their regulation of IL‐33. In fibroblasts, the concerted action of TNF‐α and IL‐1β was the strongest inducer, whereas IFN‐γ is clearly the key molecule that upregulates IL‐33 in keratinocytes with a more pronounced response of cells derived from patients with AD. Keratinocytes from patients with AD showed a markedly higher constitutive expression level of surface ST2. CD4+ T cells respond to IL‐33. Unexpectedly, IL‐33 failed to induce a significant secretion of IL‐5 or IL‐13. By contrast, high amounts of IFN‐γ were detectable if IL‐33 was added to the T‐cell receptor‐stimulated cells or in combination with IL‐12. These results suggest that IL‐33 and IFN‐γ are closely interlinked in epidermal AD inflammation. IFN‐γ induces IL‐33 in keratinocytes and IL‐33 acts on activated T cells to further increase the release of IFN‐γ, therefore contributing to drive skin inflammation towards chronic responses.     

Increased interleukin‐36γ expression in skin and sera of patients with atopic dermatitis and mycosis fungoides/Sézary syndrome

Interleukin (IL)‐36γ is expressed by keratinocytes and functions as a key initiator of inflammation in the skin. IL‐36γ expression is enhanced by tumor necrosis factor‐α and IL‐17A, having a strong association with psoriasis. In this study, we examined the role of IL‐36γ in atopic dermatitis (AD) and mycosis fungoides (MF)/Sézary syndrome (SS). Serum levels of IL‐36γ in AD patients and MF/SS patients were elevated compared with those of healthy controls. Importantly, serum IL‐36γ levels in AD patients positively correlated with Eczema Area and Severity Index and those of MF/SS patients positively correlated with serum soluble IL‐2 receptor levels. IL‐36γ mRNA levels in AD skin and MF/SS skin were significantly higher than those of normal skin. IL‐36γ mRNA levels in MF/SS skin positively correlated with IL‐17A mRNA levels. Immunohistochemical staining revealed that IL‐36γ was highly expressed in keratinocytes in lesional skin of AD and MF/SS. Taken together, our study demonstrated that IL‐36γ expression was increased in sera and skin of patients with AD and MF/SS as was reported in psoriatic patients.     

Toll‐like receptor 4 attenuates a murine model of atopic dermatitis through inhibition of langerin‐positive DCs migration

Atopic dermatitis (AD) is a common chronic inflammatory skin disease that is often associated with skin barrier dysfunction leading to a higher frequency of bacterial and viral skin infections. Toll‐like receptor (TLR) 4 on resident skin cells was involved in sensing pathogens and eliciting pathogen‐specific innate and adaptive immune responses. Previous studies have demonstrated that TLR4 was linked to AD severity in context of pathogen infection. However, the immune regulatory role of TLR4 in AD remains to be defined. We here investigated the immune regulatory function of TLR4 in AD induced by repeated epicutaneous application of a hapten, 2,4‐dinitrochlorobenzene (DNCB). Our results showed that TLR4‐deficient (TLR4^?/?) mice exhibited more severe AD symptoms than WT mice after DNCB challenge. The DNCB‐treated TLR4^?/? mice also displayed higher expression levels of inflammatory cytokines and stronger Th2 response than WT counterparts. Moreover, the skin expression of thymic stromal lymphopoietin (TSLP), an important potential contributor to allergic inflammation, was significantly elevated in TLR4^?/? mice compared with that in WT mice upon DNCB administration. Furthermore, we demonstrated that the migration of langerin‐positive dendritic cells (DCs) into draining lymph nodes was enhanced in TLR4^?/? mice following DNCB challenge, which is partially dependent on the production of pro‐inflammatory cytokine TNF‐α. Together, these results determined that TLR4 affected the hapten‐induced skin inflammation in the absence of exogenous pathogen infection, suggesting that TLR4 not only regulates infection but also may serve as a modulator of the immune response during AD development.     

IL‐24 is expressed during wound repair and inhibits TGFα‐induced migration and proliferation of keratinocytes

Please cite this paper as: IL‐24 is expressed during wound repair and inhibits TGFα ‐induced migration and proliferation of keratinocytes. Experimental Dermatology 2010; 19 : 714–722. Abstract: Interleukin (IL)‐24 is the protein product of melanoma differentiation‐associated gene 7 (MDA‐7). Originally identified as a tumor suppressor molecule, MDA‐7 was renamed IL‐24 and classified as a cytokine because of its chromosomal location in the IL‐10 locus, its mRNA expression in leukocytes, and its secretory sequence elements. We previously reported that IL‐24 is expressed by cytokine‐activated monocytes and T lymphocytes. Here, we show that IL‐24 is expressed in keratinocytes during wound repair. Paraffin‐embedded tissues prepared from human skin sampled at days 2, 6, and 10 after wounding were examined by immunohistochemistry for the expression of IL‐24. Protein expression was detected in the keratinocyte population with maximum expression at days 2 and 6, and no expression by day 10 (four of four subjects). In vitro studies showed that cytokines involved in wound repair, most notably transforming growth factor α (TGFα), TGFβ, IFNγ, and IFNβ, upregulated IL‐24 protein expression in normal human epidermal keratinocytes (NHEKs). Examination of the function of IL‐24 in both in vitro wound repair and migration assays demonstrated that IL‐24 inhibits TGFα‐induced proliferation and migration of NHEKs. These data support the hypothesis that IL‐24 functions during an inflammatory response in the skin by inhibiting the proliferation and migration of keratinocytes.     

S‐allyl cysteine inhibits TNF‐α‐induced inflammation in HaCaT keratinocytes by inhibition of NF‐ κB‐dependent gene expression via sustained ERK activation

Tumor necrosis factor‐α (TNF‐α)‐induced keratinocyte inflammation plays a key role in the pathogenesis of multiple inflammatory skin diseases. Here we investigated the anti‐inflammatory effect of S‐allyl cysteine (SAC) on TNF‐α‐induced HaCaT keratinocyte cells and the mechanism behind its anti‐inflammatory potential. SAC was found to inhibit TNF‐α‐stimulated cytokine expression. Further, SAC was found to inhibit TNF‐α‐induced activation of p38, JNK and NF‐κB pathways. Interestingly, SAC was found to differentially regulate ERK MAP kinase in cells. TNF‐α‐induced transient ERK activation and SAC treatment resulted in sustained ERK activation both in the presence and absence of TNF‐α. Additionally, SAC failed to inhibit the TNF‐α‐induced expression of the pro‐inflammatory cytokines TNF‐α and IL‐1β when cells were treated with the MEK inhibitor PD98059, suggesting that the anti‐inflammatory effect of SAC is via sustained activation of the ERK pathway. Since ERK activation has been reported to negatively regulate NF‐κB‐driven gene expression and we find that SAC activates ERK and negatively regulates NF‐κB, we investigated whether there existed any crosstalk between the ERK and the NF‐κB pathways. NF‐κB‐dependent reporter assay, visualization of the nuclear translocation of NF‐κB‐p65 subunit and determination of the cellular levels of I‐κB, the inhibitor of NF‐κB, revealed that SAC inhibited TNF‐α‐induced NF‐κB activation, and PD98059 treatment reversed this effect. These results collectively suggest that SAC inhibits TNF‐α‐induced inflammation in HaCaT cells via a combined effect entailing the inhibition of the p38 and the JNK pathways and NF‐κB pathway via the sustained activation of ERK.     

Tropisetron via α7 nicotinic acetylcholine receptor suppresses tumor necrosis factor‐α‐mediated cell responses of human keratinocytes

Tropisetron is a serotonin receptor (5‐HT‐R)‐modulating agent and approved as an antiemetic for patients undergoing chemotherapy. In the gut, it acts via specific serotonin receptors, 5‐HT₃‐R, to elicit its beneficial effects against nausea. We investigated whether tropisetron can affect inflammatory cell responses of human primary epidermal keratinocytes (NHK) which are key cells in the regulation of skin homoeostasis. Tropisetron significantly and dose‐dependently suppressed tumor necrosis factor (TNF)‐α‐mediated mRNA expression and protein secretion of interleukin (IL)‐6 and IL‐8 in these cells. This effect of tropisetron was independent of p65/NF‐κB as shown by various NF‐κB signal transduction read‐outs. Importantly, the anti‐inflammatory tropisetron effect on NHK was neither mediated by 5‐HT₃‐R nor 5‐HT₄‐R since these receptors were absent in NHK. In contrast, NHK expressed α7 nicotinic acetylcholine receptors (α7nAchR) which previously were found to bind tropisetron. The α7nAchR antagonist α‐bungarotoxin neutralized, whereas AR‐R17779, a specific α7nAchR agonist, mimicked the suppressive effect of tropisetron on TNF‐α‐mediated IL‐6 and IL‐8 expression in NHK. Our findings suggest that tropisetron and probably other α7nAchR‐activating agents could be useful for the future therapy of inflammatory skin diseases.     

Epidermal keratinocytes sense dsRNA via the NLRP3 inflammasome,mediating interleukin (IL)‐1β and IL‐18 release

Skin epidermis, in addition to its barrier function, is able to actively sense harmful pathogens using pattern recognition receptors. In immune cells, the nucleotide‐binding oligomerization domain, leucine‐rich repeat and pyrin domain containing 3 (NLRP3) inflammasome can mediate innate immunity against viral infection via a mechanism involving viral dsRNA recognition. Epidermal keratinocytes express NLRP3 inflammasome, which can sense contact sensitizers and mite allergens, leading to pro‐interleukin (IL)‐1β and pro‐IL‐18 cleavage into their active forms. Skin often faces viral infection. However, it is unknown whether viral dsRNA can be detected by the keratinocyte NLRP3 inflammasome. We transfected polyinosinic:polycytidylic acid (poly I:C), a synthetic viral dsRNA analogue, into cultured primary human keratinocytes at the aid of Lipofectamine 2000, and found that transfected poly I:C activated caspase‐1 and induced caspase‐1‐dependent release of IL‐1β and IL‐18, which were suppressed on transfection with NLRP3 siRNA. The activation of keratinocyte NLRP3 inflammasome by transfected poly I:C was dependent on dsRNA‐induced protein kinase (PKR) activation, and priming with type I interferons upregulated NLRP3 inflammasome activation through promoting PKR activation in poly I:C‐transfected keratinocytes. In conclusion, the NLRP3 inflammasome can act as a sensor of dsRNA in epidermal keratinocytes, which may be important in both skin innate immune defense against viral infection and skin inflammation.     

TNFα‐ and IL‐17A‐mediated S100A8 expression is regulated by p38 MAPK

The antimicrobial peptide S100A8 is known to be upregulated in lesional psoriatic skin compared with non‐lesional psoriatic skin and is believed to play a role in the pathogenesis of psoriasis. However, little is known about the signalling pathways involved in the regulation of S100A8 expression. Using quantitative real‐time RT‐PCR analysis, we demonstrated that stimulation with TNFα and IL‐17A in combination resulted in a significant and synergistic induction of S100A8 mRNA in human keratinocytes. TNFα and IL‐17A also induced the S100A8 promoter activity synergistically. This was demonstrated by a gene reporter assay in cells transfected with a luciferase plasmid construct, consisting of 3502 base pairs of the human S100A8 promoter. The TNFα‐ and IL‐17A‐mediated induction of S100A8 mRNA and protein was mediated by a p38 MAPK‐dependent mechanism, as demonstrated by the use of a p38 MAPK inhibitor. Finally, adalimumab treatment for patients with psoriasis significantly decreased S100A8 mRNA at day fourteen after start of treatment, but not at day four. Taken together, this study demonstrates that the p38 MAPK signalling pathway plays a key role in the TNFα‐ and IL‐17A‐induced expression of S100A8 in cultured human keratinocytes.     

IL‐33 is secreted by psoriatic keratinocytes and induces pro‐inflammatory cytokines via keratinocyte and mast cell activation

IL‐33 is a novel pro‐inflammatory cytokine and ligand for the orphan receptor ST2. Although originally defined as an inducer of Th2‐mediated responses, IL‐33 was recently found to be involved in arthritis, a Th1/Th17‐mediated disease. Here, we assessed the ability of IL‐33 to promote inflammation via mast cells (MCs) and keratinocytes (KCs) activation in psoriasis. IL‐33 resulted elevated in the skin but not in the serum of psoriasis patients. IL‐33 was secreted by psoriasis KCs and HaCaT cells after TNF‐α stimulation. In HMC‐1, TNF‐α, but not IL‐17, could induce a robust increase in IL‐33 expression. In HaCaT cells, TNF‐α was able to induce IL‐6, MCP‐1 and VEGF, and the addition of IL‐33 reinforced these increases. TNF‐α + IL‐33 combination showed similar results in primary KCs and ex vivo skin organ culture. In conclusion, our study suggests that IL‐33 may be involved in psoriasis biology via MCs and KCs.     

Adipose‐derived stem cells attenuate atopic dermatitis‐like skin lesions in NC/Nga mice

There is an unmet need in novel therapeutics for atopic dermatitis (AD). We examined the effects of autologous adipose‐derived stem cells (ADSCs) on AD‐like skin lesions induced by the application of 2,4‐dinitrochlorobenzene (DNCB) in NC/Nga mice. Autologous ADSCs and ADSC‐conditioned medium (ADSC‐CM) were injected intralesionally three times. Clinical severity and histopathologic findings were compared in sham naïve control, saline‐treated, ADSC‐treated, ADSC‐CM‐treated and 2.5% cortisone lotion‐applied animals. The severity index, skin thickness, mast cell number, as well as expression levels of thymic stromal lymphopoietin, CD45, chemoattractant receptor‐homologous molecule, chemokine ligand 9 and chemokine ligand 20 were significantly lower in mice treated with ADSC, ADSC‐CM, or 2.5% cortisone lotion. Tissue levels of interferon‐γ as well as serum levels of interleukin‐33 and immunoglobulin E levels were also decreased in those groups. We conclude that autologous ADSCs improved DNCB‐induced AD‐like skin lesions in NC/Nga mice by reducing inflammation associated with Th2 immune response and interferon‐γ.     

DAMP molecules S100A9 and S100A8 activated by IL‐17A and house‐dust mites are increased in atopic dermatitis

S100A9 and S100A8 are called damage‐associated molecular pattern (DAMP) molecules because of their pro‐inflammatory properties. Few studies have evaluated S100A9 and S100A8 function as DAMP molecules in atopic dermatitis (AD). We investigated how house‐dust mites affect S100A9 and S100A8 expression in Th2 cytokine‐ and Th17 cytokine‐treated keratinocytes, and how secretion of these molecules affects keratinocyte‐derived cytokines. Finally, we evaluated expression of these DAMP molecules in AD patients. S100A9 expression and S100A8 expression were strongly induced in IL‐17A‐ and Dermatophagoides (D.) farinae‐treated keratinocytes, respectively. Furthermore, co‐treatment with D. farinae and IL‐17A strongly increased expression of S100A9 and S100A8 compared with D. farinae‐Th2 cytokine co‐treatment. The IL‐33 mRNA level increased in a dose‐dependent manner in S100A9‐treated keratinocytes, but TSLP expression did not change. S100A8/A9 levels were also higher in the lesional skin and serum of AD patients, and correlated with disease severity. Taken together, S100A9 and S100A8 may be involved in inducing DAMP‐mediated inflammation in AD triggered by IL‐17A and house‐dust mites.     

CCL7 contributes to the TNF‐alpha‐dependent inflammation of lesional psoriatic skin

Chemokines are small chemotactic proteins that have a crucial role in leukocyte recruitment into tissue. Targeting these mediators has been suggested as a potential therapeutic option in inflammatory skin diseases such as psoriasis. Using quantitative RT‐PCR, we found CCL7, a chemokine ligand known to interact with multiple C‐C chemokine receptors, to be markedly increased in lesional psoriasis as opposed to atopic dermatitis, lichen planus, non‐lesional psoriatic and normal control skin. Surprisingly, this increase in CCL7 mRNA expression exceeded that of all other chemokines investigated, and keratinocytes and dermal blood endothelial cells were identified as its likely cellular sources. In an imiquimod‐induced psoriasis‐like mouse model, CCL7 had a profound impact on myeloid cell inflammation as well as on the upregulation of key pro‐psoriatic cytokines such as CCL20, IL‐12p40 and IL‐17C, while its blockade led to an increase in the antipsoriatic cytokine IL‐4. In humans receiving the TNF‐α‐blocker infliximab, CCL7 was downregulated in lesional psoriatic skin already within 16 hours after a single intravenous infusion. These data suggest that CCL7 acts as a driver of TNF‐α‐dependent Th1/Th17‐mediated inflammation in lesional psoriatic skin.     

Interleukin‐33 modulates the expression of human β‐defensin 2 in human primary keratinocytes and may influence the susceptibility to bacterial superinfection in acute atopic dermatitis

Background Interleukin (IL)‐33 is a member of the IL‐1 family and has been implicated in Th2‐driven allergic diseases such as atopic dermatitis (AD) and asthma. The principal Th2 cytokine IL‐4, found highly expressed in acute allergic eczema, is known to downregulate human β‐defensin 2 (hBD2) expression in human keratinocytes and this is associated with superinfection in patients with AD. Objectives To investigate the effect of IL‐33 on the expression of hBD2 in human keratinocytes. Methods hBD2 production by stimulated keratinocytes was measured by enzyme‐linked immunosorbent assay. Results Our results showed that serum is a very potent inducer of hBD2 and 2·5% human serum was much more potent in inducing hBD2 than 20 ng mL^?1 of tumour necrosis factor‐α. Interestingly, serum from patients with AD showed an impaired ability to induce hBD2 in normal keratinocytes. IL‐33 significantly downregulated serum‐induced hBD2. The downregulatory capacity of IL‐33 was found to be 1·5‐ to 2‐fold weaker compared with IL‐4. Conclusions Our data suggest that IL‐33 can significantly contribute to the decreased expression of hBD2 in acute eczematous reaction clinically characterized by spongiosis and oozing – thus indicative for contact of the epidermis with serum components.     

Investigation of cytokine levels and their association with SCORAD index in adults with acute atopic dermatitis

Background Atopic dermatitis (AD) is a chronic inflammatory skin disease with increasing frequency over the last decades, especially in adults. Cytokines orchestrate atopic skin inflammation. Objectives The aim of this study was to compare serum levels of cytokines in adult patients with acute AD (AD1) with other groups of AD patients and controls and investigate the possible association between such cytokines and disease severity. Methods We measured cytokine levels using flow cytometry in 21 adult patients with acute AD, 12 adults with chronic AD, 10 children with acute AD and 10 healthy adults. Results Flow cytometry analysis of cytokines revealed that interleukin 10 (IL‐10), IL‐6, interferon γ (IFN‐γ) and IL‐4 levels were significantly decreased in AD1 group compared with controls, whereas IL‐2 and tumour necrosis factor (TNF) did not differ. Comparison of AD1 group with adults chronic phase group showed that IgE, eosinophil and IL‐2 levels remained unaltered, whereas IL‐10, IL‐6, IFN‐γ, IL‐4 and TNF were significantly decreased. SCORAD and IgE levels were significantly increased, IL‐10, IL‐6 and IFN‐γ were decreased and TNF, IL‐2, IL‐4 and eosinophil levels remained unchanged in AD1 group compared with children acute phase group. Within AD1 group correlation analysis revealed that IgE and TNF levels were significantly associated with AD severity. Coefficient of determination analysis revealed that TNF and IgE levels could explain 49.14% and 35.28% of the variance of SCORAD. Conclusions These data indicate that serum IgE and TNF levels correlate with AD severity and that serum cytokines are downregulated in AD1 group. Further studies are clearly needed to elucidate cytokines’ role in adults with AD .